As is well-known in the industry, an integrated circuit package is used which comprises an integrated circuit ceramic module and a printed circuit board. Input-output (I/O) pins are mounted in holes in a ceramic substrate and are connected to metallized circuitry on the surface of the substrate. The I/O pins are soldered into plated-through holes in the printed circuit board to electrically interconnect the module and board. This type of interconnection system is costly to manufacture and assemble. Also, it has the disadvantage that when the module and board are interconnected a thermal cycle is employed during which a difference of expansion occurs between the ceramic substrate and the circuit board. This causes pins to crack or break their solder connection with the plated-through holes which results in circuit problems.
In present day technology, there is an ever-increasing demand for greater input-output density. This means a greater number of pin holes, pins and through holes. If in increasing the number of pin holes, holes are made near the edge of the ceramic substrate, they will have to be made smaller to prevent cracking of the ceramic. This means that smaller pins would be required, which raises a problem.
It became evident that it would be desirable to provide a different type of interconnection system which would provide high density and better reliability at a lower cost.